Signaling-circuit



P. HACKETT.

SIGNALING CIRCUIT.

APPLICATION man JUNE 21. I919.

Patented July 27, 1920.

3 SHEETSSHEET I.

INI/E/VTOR P. J. HACKETT. SIGNALING CIRCUIT.

APPLICATION FILED JUNE 21. 1919.

1,347, 49; Patented Ju1y 27, 1920.

3 SHEETS-SHEET 2- v WITNESSES. l/Vl/E/VTOI? P. J. HACKETT.

SIGNALING CIRCUIT.

APPUCATION FILED JUNE 21, 1919.

1,347,849. a t d uly 27, 1920.

3 SHEETS-SHEET 3.

WiTNES ES: l/VVE/VTOR w BY ,4 TTOR/VEV UNITED STATES. PATENT OFFICE.

PAUL JQ AoKET'noE EATTLE, WASHINGTON, ASsIGNon To UNIVERSAL are POWERTELEPHONE c0 0E SEATTLE, WASHINGTON.

SIGNALING-CIRCUIT.

Applicationfiled June 21,

T 0 all whom it may concern:

Be it known that 1, PAUL J. HAG ETT, a citizen of the United States,residing at Seattle, in the county of King and State of \Vashington,have invented a certain new and useful Improvement inSignaling-Circuits, of which the following is a full, clear, concise,and exact description 7 This invention relates to the circuitarrangement of a telephone substation, and more particularly totelephone substations in combination with a telephone line over whichtwo-way communication is to be established.

The object of this invention is to provide a circuit arrangement of thesubstation apparatus in a single line circuit two-way communicationsystem such that each substa tion will be free from side tone, and, willalso give a maximum ratio of received to transmitted energy consistentwith the requirements necessary to secure freedom fromside tone. I

In order to attain the objects or this invention several requirementsmust be satisfied. In a single line circuit two-way communicatingsystem, it is impossible to secure freedom from side tone without theuse of; an auxiliary resistance element at each sub-j station inaddition to the regular equipment of a transmitter, a receiver, andinduction coils. In eliminating the side tone while transmitting, theauxiliary resistance receives the energy which would otherwise go to thereceiver. One requirement therefore, is: (l) The receiver andtransmitter must be conjugate, that is the'receiver must not be affectedby energy originating in the transmitter of the same substation. Otherrequirements are: for a line of given impedance the energy delivered bythe transmitter must be a maximum; the energy delivered by the line tothe substation must be a maximum; (4;) the line and auxiliary resistancemust be conjugate in order that none of the energy delivered by the lineto the substation shall be wasted in the resist ance while receiving.

The substation of my invention is provided with a transmitter, areceiver, an auxiliary resistance and necessary transformers to soconnect and relate the component elements to each other and to the linethat the above mentioned requirements are fulfilled.

The specific embodiment of my invention Specification of Letters Patent.

1919. Serial No. 305,755.

is illustrated in the accompanying drawings in which Figure 1 is adiagram ofthe fundamental arrangement of the substation apparatus, theremaining drawings illustrating modifications of Fig. 1. Figs. 2 and 3are diagrams showing the direction of ourrent'fiow in the substation ofF ig.- 1 while transmitting and receiving respectively. Fig. 4, showsthe substation of my invention adapted for the use of a differentialtransmitter. Figs. 5 and 6 show the substation of my invention adapted.for use in common battery systems using a differential transmitter. Theuse of a differential transmitter in common battery systems makesnecessary'the impedance coils ZZ' and Z. Fig. 7 is a diagramillustrating a modification of the substation of Fig. 1 in that thetransmitter and receiver are inter-changedso a sto be suited for commonbattery systems using a simple transmitter. Condenser (l may be placedin serieswith a Winding N to prevent the flow of direct current throughthis path- Figs. 8 and 9 are-diagrams illustrating the flow of currentinthe-substation of Fig. 7 while transmitting and receivingrespectively.

Referring to Fig.1, L is a line connected to a substation comprising a'transmitter T, a receiver R, an auxiliary resistanceX, and two inductioncoils having twowindings each N N and N N respectively. The receiver. R,and auxiliary resistancefX, are

serially connected across the line L by termi= nals 5, 6, 7, was.WVinding N ot' anin-i duction coil is in bridge of line L, and-winding Nof the other induction coil is in bridge of resistance X. The remainingwindings N and N of the induction coils, and the transmitter T, form. aseparateserial circuit being inductively associated with the otherelements by means of the induction coils.

The operation of the substation during transmission is shown in Fig. 2.Upon speaking into the transmittertheaction isequivalent to generatingan alternating voltage in the transmitter. Considering, then, that thetransmitter is a source of alternat- Patented Jury 27, 1920'.

ing current, a current I, will flow in the designed, no current willflow through the;

receiver circuit since the voltages acting in this circuit are equal andopposite. vThe current flow during reception is shown in Fig. 3 and theaction is as follows: An alternating voltage applied to the linewill'supply a line current I i to the substation, this current dividingat terminal 6, a part 1 flowing through the receiver R, winding N andback to the line through terminal 5: another part I, flowingthroughwinding N Current'l in winding N induces a current 1 in the transmittercircuit. The substation beingproperly designed, the magneto-motive-lorce of winding Y isiequal and opposite to themagneto-motiveforce of winding N consequently, neglecting theresistancedrops-in winding N there will be no voltage drop across winding'N and nocurrent will flow through the auxiliary resistance X.

. The necessary design formulae for the properproportioning of thevarious elements and transformer ratios to meet the above requirementsmay be derived as follows:

Let the number of turns of windings N N N and N bedenoted by n n a, andn respectively; and .let the current and resistance of the transmitter,receiver, auxiliary resistance and line be denoted by I 1 1,, I and R RR respectively. Inderiving these formulae the transformer windings willbe assumed to have negligible resistance and to be closely coupled. Theline impedance and the impedance of the component elements will also beassumed to be pure resistance, since any reactance effect may beneutralized if desired. The first requirement is that the transmitterand 'receiver must be conjugate, that is no current must fiowin'thereceiver circuit while transmitting. Referring to Fig. 2, assume, then,tliatno current flows through the receiver, and the followingrelationsmust be satisfied,

Another requirementis that the auxiliary resistance must: be conjugatet0 the line While receiving. Referring to Fig. 3, the followingrelations must be true in vorder for no currentto'flow 1n the auxiliaryresistance while receiving:

Y I 2 's i i V 7 721 v and I R --)=I,R a, q e

a n n whence R =R -Z- Z I (5) Another requirement is that the line mustsupply maximum energy to the substation. It is a fundamental principlethat the re-' sistance of the terminal apparatus connected '8 to a llnemust be equal to the resistance of the line for maximum. delivery ofenergy, neglecting any reactance effect. For maxi mum out-put, then, theimpedance of the V substation as seen from the line must be equal to theimpedance of the line or, r ab m' I Where 7 =11, and b=R 9o 2 I 01' iR4: 2

t) l a 1 1 substituting equation (5) Another requirement is that thetransmitter must have maximum output, which means that the resistance ofthe circuit supplied by the transmitter must be equal to the re.-sistance of the transmitter itself, or

Collecting equations (4:), (6), and (7) we have convenient designformulae expressing the impedance of the various elements in terms ofthe line impedance and the transformer ratios;

Fig. 7 is a modification ofthe substation of my inventionadapted for useon common battery. systems.

The operation during transmission is shown in Fig. 8 and is as follows;the action of the transmitter supplies alternating current to the lineL, and auxiliary resistance X, in series, the instantaneous direction ofcurrent fiow being indicated by the arrows. \Vindings i and N are inbridge of the line and auxiliary resistance respectively, and theyinduce voltages inwindings N and N respectively. -The substation beingproperly designed andv so connected that the voltages-induced inwindings N and N will be'equal and opposite, andno current Will flow inthe receiver circuit.

The action while receiving is shown in Fig.9 and is the same as for Fig.3 except that the receiver and transmitterare interchanged. The designformulae for this modification are very similar to those for Fig. 1, andmay be derived in a similar manner since the only difference is aninterchange-of position of'transmitter. and re-- ceiver. r

The design formulae for Fig." 7 are:

Iii-Bil mm) R3 4 n n It can readily be seen that modifications of thesubstation of my invention, other than those which I have here shown,can be had by simply inter-changing the positions of the variouselements, and consequently my invention is not to be limited to theparticular forms shown. It will be understood, also, that, since idealconditions have been assumed, I do not desire to limit the design of thesubstation of my invention to the design formulae set forth in thisspecification, but may modify the design to allow for actual conditionsfound in practice. The designfformulae set forth in this specificationhave been given to show only the fundamental relations existing in thesubstation of my invention.

\Vhat I claim is:

1. In a two way signaling system, the combination of two transformerseach having a plurality of windings, and four coniponent elementsconsisting, respectively, of a circuit for the transmission andreception of signals, a receiving circuit proper, a balancing circuitproper, and a transmitting circuit, three of said component elementsforming a serial circuit, one winding each of said transformers bridgingseparately two of said component elements in said serial circuit, theremaining fourth component elementforming another serial circuit withwindings of said transformers, said serial circuit being inductivelyrelated to first named serial circuit, said elements being soproportioned and related that the impedance of the combinationcomprising said first named circuit, said receiving circuit proper, saidbalancing circuit and said transformers, as seen from said transmittingcircuit proper, is equal to the impedance of said transmitting circuitproper.

2. In a two way signaling system, the combination of two transformerseach having a plu 'ality of windings, and four component elementsconsisting, respectively, of a circuit for the transmission andreception of signals, a receiving circuit proper, a balancing circuitproper, and a transmitting circuit, three of said component elementscombination of-two transformers'each having a plurality of windings, andfour component elements consisting respectively, of a circuit for thetransmission"and'reception of signals, arec'eiving' circuit proper, abalancing circuit proper, and a transmitting circuit, three of saidcomponent elements forming a serial circuit, one winding each of saidtransformers bridging separately two of'said component elements insa'idserial circuit, the remaining fourth component element forming anotherserial circuit with windings'of said transformers, said serial circuitbeing inductively related to first named serial circuit, said elementsbeing so proportioned and related that said, balancing circuit and saidfirst named circuit are conjugate.

l. In a two way signaling system, the

combination of two transformers each having a plurality of windings, andfour component elements consisting, respectively, of a circuit for'thetransmission and reception of signals, a receiving circuit proper, abalancing circuit proper, and a transmitting circuit, three of saidcomponent elements forming a serial circuit, one winding each of said"transformers bridging separately two of said component elements insaid'serial circuit, the remaining fourth component element forminganother serial circuit with windings of sa1d transformers, said serialcircuit being inductively related to first named serial" circuit, saidelements being so proportioned and related that the-impedance of thecombination comprising said transm ttlng cn'cult proper, said receiv ngcircuit proper, said balancing circuit and said transformers,as seenfrom first named circult, is

equal to the impedance of firstv named circuit.

5. In a two way signaling system, the combination of two transformerseach havinga plurality of windings, and four component elementsconsisting, respectively, of a circuit for the transmission andreception of signals, a receiving circuit proper,a balancing circuitproper, and, a transmitting circuit, three of said component elementsforming a serial circuit, one winding each of said transformers bridgingseparately two of said component elementsin said se-V rial circuit, theremaining fourth component element forming another serial circuit withwindings of said transformers, said serial circuit being inductivelyrelated 'to'first named serial circuit, said elements being soproportioned and related that said transmitting circuit and saidreceiving circuit are conjugate; said. first named circuit and saidbalancing circuit are conjugate, the; im-

pedance of the combination comprising said first named circuit, saidreceiving circuit proper, said balancing circuit and said transformers,as seen from said transmitting circuit proper, .is' equal to theimpedance of said transmitting circuit; and the impedance of thecombination comprising said transmitting circuit proper, said receivingcircuit proper, said balancing circuit and said transformers, as seenfrom said first named circuit, is equal to the impedance of said firstnamed circuit. V

6. A telephone apparatus, comprising a line, a transmitter, a receiverand an auxiliary resistance, three of said elements forming aserialcircuit, two induction coils having two windings each, one winding eachof said induction coils bridging separately two of said elements in saidserial circuit, the

fourth element and the remaining two windings of said 1nduct1on co1lsform ng a separate serial circuit," said circuit being inductivelyassociated with the first mentioned circircuit, the parts being soproportioned, and

the connections such, that the transmitter supplies maximum energywithout absorption of energy by thereceiver,

twee

.8. A telephone apparatus, comprising a l1ne, a transmitter, a receiverand a-n auml iaryresistance, threeof said elements forming a serialcircuit, two induction coils havthe connections such, that substantiallynone of the energy supplied by the transmitter shall be absorbed by thereceiver.

9. A telephone apparatus, comprising a ,line, a transmitter, a receiverand anzuixiliary resistance, three of said elements formingia serialcircuit, two induction coils having two windings each, one winding'eachof said induction coils bridging separately two of said elements in saidserial circuit, the fourthelement and the remaining two windings ofsaidinduction coils forminga separate serial circuit, said circuit beinginductively associated with the first mentioned circuit, the parts beingso proportioned, and the connections such, that the transmitter suppliesmaximum effective energy.

10. A telephone apparatus, comprising'a line, a transmitter, a receiverand an auxiliary resistance, three of said elements forming a serialcircuit, two induction coils having two windings each, one windingeachof said induction coils bridging separately two of said elementsinsaid serial circuit, the fourth element and the remaining two windingsof said induction coils forming a separate serial circuit, said circuitbeing inductively associated with thefirst mentioned circuit, the partsbeing so proportioned, and the connections such, that maximum energy isabsorbed by the receiver from the line when receiving. r a

11. A telephone apparatus, comprising a line, a transmitter, a" receiverand an auxiliary resistance, three of said elementsv forming a serialcircuit, two induction coils having two windings each, one winding eachof said induction coils bridging separately two of said elements in saidserial circuit, the fourth element and the remaining two windings ofsaid inductioncoils forming a sepasaid induction coils bridgingseparately two of said elements in said serial circuit, the fourthelement and the remaining two Windings cf said induction coils forming aseparate serial circuit, said circuit being inductively associated withthe first mentioned circuit, the parts being soproportioned, and theconnections such, that the transmitter supplies maximum energy to theline Without absorption of energy, by the receiver when the apparatus istransmitting, and maximum energy is absorbed by the receiver from theline WhGl'l'thG apparatus is receiv ing, Without absorption of energy bysaid resistance.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing Witnesses, this thirteenth day of June,1919.

PAUL J. HACKETT.

lVitnesses H. J. FARRAR, C. B. MoCoY.

